1. Field of the Invention
The present invention relates to a turn signal apparatus having a turn lever operable for indicating a change in direction of a forward moving vehicle and which is adapted to automatically return to its neutral position when a steering shaft is rotated in an opposite direction.
2. Background Information
Self-cancelling devices for turn signal switches are generally arranged such that a bracket formed in such a manner as to surround a steering shaft is swingably supported on a base. A turn lever is fixed to one side portion of the bracket, and a ratchet of a self-cancelling device is disposed on an opposing side thereof. When the bracket is displaced by a turn lever to the left-turn indicating position or right-turn indicating position, a ratchet pawl is positioned in a rotating path of a projectin of a cancellation cam. Then, when the cancellation cam is rotated in an opposite direction to the direction of the turn lever by the operation of the steering wheel in a returning direction, the cancellation cam presses the ratchet pawl, thereby allowing the bracket and, hence, the turn lever, to be returned to their neutral positions. In the above-described arrangement, however, since the bracket is formed in such a manner as to surround the steering shaft, there is a problem in that the apparatus becomes large in size.
A conventional apparatus disclosed in Japanese Utility Model Laid-Open No. 199146/1982 is known in which improvements were made on this aspect (see FIG. 6). A bracket 3 formed of a plastic is swingably supported about a shaft 2 so that the bracket 3 is located on one side of the steering shaft 1. The arrangement is such that the bracket 3 is rotated from the neutral position to the right-turn indicating position or the left-turn indicating position by means of a turn lever 4 secured to the side of the bracket 3 most distant from the side where the steering shaft 1 is located. In addition, an engaging member 5 having an end 5a oriented toward the steering shaft 1 side is movably provided on the bracket 3 at a position on the steering shaft 1 side. A pair of elastic deformable engaging arms 6 are integrally provided on the bracket 3. These engaging arms 6 are opposed to the other end 5b of the engaging member 5. The arrangement is such that when the bracket 3 is rotated from the neutral position to the right-turn indicating position or the left-turn indicating position, one end 5a of the engaging member 5 is located in the rotating path of the projection 1a of the steering shaft 1. When the steering shaft 1 is rotated in the same direction as the turning direction, the other end 5b of the engaging member 5 is swung between the engaging arms 6, 6. When the steering shaft 1 is rotated in the opposite direction to the turning direction, the projection 1a is brought into contact with one end 5a of the engaging member 5, thereby allowing the other end 5b to be engaged with either of the engaging arms 6. Hence, the bracket 3 is returned to its neutral position.
In the above-described arrangement, however, when the turn lever 4 is self-canceled, the other end 5b of the engaging member 5 is arranged to move the engaging arm 6 of the bracket 3. For this reason, a large load weighing, for example, 8 kg is required for rotating the engaging member 5, so that a large frictional force acts between the engaging member 5 on the one hand, and the projection 1a and the engaging arm 6 on the other, with the result that the engaging member 5 is liable to undergo abrasion and is therefore inferior in terms of durability. In addition, there has been another drawback in that a large manipulating force for returning the steering wheel is required.